A World Health Organization doctor is rejecting assertions that unsafe injections are a major source of HIV infections in Africa, arguing the infection is mainly spread through heterosexual sex. The findings are to appear in the medical journal The Lancet on Saturday.

The World Health Organization says it strongly disagrees with claims by an American scientist that most HIV infections in sub-Saharan Africa result from unsafe injections. An agency AIDS expert, who is the lead author of The Lancet article, Dr. George Schmid, says only a fraction of HIV transmission in Africa is caused by dirty needles.

"We find there is no compelling evidence that unsafe injections are a major mode of HIV transmission in sub-Saharan Africa," he said. "We agree, however, that unsafe injections are an unacceptable practice and that efforts should be increased to detect and reduce exposure of patients to any blood-borne infection in health-care settings."

During the past year, a group of researchers headed by American scientist, David Gisselquist, claimed that up to 40 percent of HIV infections in Africa are caused by contaminated needles used during medical treatment.

The World Health Organization estimates that between 25 million and 28 million people in sub-Saharan Africa are infected with HIV, the virus that causes AIDS. WHO says approximately 90 percent of infections in adults are caused by sexual transmission.

The Gisselquist group argued that the widespread re-use of unsterilized needles and syringes is the major mode of HIV spread in Africa. But Dr. Schmid says unsafe injections are not as frequent as the Gisselquist group claimed. Furthermore, he adds, this theory does not take into account the way in which injections are used in practice.

"For instance, that injections are largely given intra-muscularly, that intra-muscular injections are infrequently contaminated by blood, or even HIV, when used on an HIV-positive patient, and that the common practice of washing, heating, and drying of syringes and needles when re-used dilutes and destroys any HIV that might have originally contaminated the needle or syringe," he said.

The World Health Organization estimates that only about 2.5 percent of HIV cases in Africa are caused by unsafe injections.

Dr. Schmid says it is important to set the record straight on the mode of transmission, because this directly affects the way AIDS prevention programs are structured. For example, he notes HIV in Russia and Eastern Europe is mainly spread through intravenous drug users. Therefore, prevention programs there discourage the use of dirty needles.

Similarly, he says, the focus in sub-Saharan Africa should be on programs that prevent transmission through heterosexual sex, rather than contaminated needles.